The direct-current (DC) distributed power generation system is increasingly popular due to its characteristics of high-efficiency and easy-to-control. DC power distribution and AC/DC hybrid power distribution is a trend of development in the future. The DC transformer is a key device for DC power distribution. The isolation type bidirectional full-bridge DC/DC converter is a typical scheme of a DC transformer, duo to its benefits of a symmetric structure, a bidirectional power transmission capability, and the soft switching is easy to realize and the like. The isolation type bidirectional full-bridge DC/DC converter is an important device for achieving the voltage level conversion and the galvanic isolation in a DC power distribution system.
When the isolation type bidirectional full-bridge DC/DC converter is applied to a DC power distribution system and used as a DC transformer, it can easily access the DC distributed generations. However, due to the intermittent and random characteristics of the distributed generations and the fluctuation of loads, the system may alter between the following two working conditions. One condition is that the high-voltage-side sub-network provides voltage support to the low-voltage-side sub-network, the other condition is that the low-voltage-side sub-network provides voltage support to the high-voltage-side sub-network. At the circumstance, a corresponding port voltage control strategy needs to be designed for the isolation type bidirectional full-bridge DC/DC converter. The traditional port voltage control method commonly controls the voltage at the high-voltage side or the low-voltage side to be constant. However, by this method, to achieve mutual voltage support between the two sub-networks of high and low voltage, one should design two voltage controllers of high and low voltage, and switch between the two controllers according to the system states. However, monitoring the system states can increase the system complexity, the cost is also increased, and the system stability may degrade due to the controller switching.
The disclosure aims at the situation that mutual voltage support may be carried out between the high and low voltage sides, and designs a constant-voltage-gain isolation type bidirectional full-bridge DC/DC converter. With a unified control mode, it establishes a seamless connection between the high and low DC networks, and can play an important role in the development of DC power distribution.